The present invention relates to an image projection system for projecting an image, such as a video image, on a screen or the like.
In the case of a single plate image projector having a single image display device, images of each color channel of RGB are time-divisionally displayed on the image display device. The color lights of RGB are irradiated on the image display device in synchronism with the display timings, and projected as a color image onto a screen. A three primary colors filter (dichroic filter) for producing three primary colors of RGB has been used in the conventional single plate projector. The three primary colors filter is constructed such that a disc is circumferentially divided into three segmental areas, and those segmental areas are colored with RGB colors (in some type of the filter, a transparent segmental area is secured). The filter is rotated in front of the white rays of light to sequentially generate RGB colored rays of light.
In the RGB light generating system using the three primary colors filter, the transmission spectrum characteristics of the three primary colors filter are not ideal. Therefore, it is impossible to extract pure color lights of RGB, and it is very difficult to make the correct color reproduction. Further, it is difficult to synchronize the mechanical rotation of the filter with the electrically displaying of the image. In this circumstance, an irregular rotation of the filter and an out-of-sync phenomenon occur, possibly causing the lowering of a color resolution and the color shift.
Attempt to rotate the filter in an in-sync state will cause a color flicker since the limit of the rotational speed is low, and the RGB colors are not mixed and hence separately seen.
A motor drive mechanism for rotating the filter has problems with its durability, and in addition, causes noise and heat generation.